10. Young female ballet dancers and gymnasts sometimes fail to maintain good eating habits caused by the desire to be as thin as possible. (D) Because they desire to be as thin as possible, young female ballet dancers and gymnasts sometimes fail to maintain good eating habits. (E) Young female ballet dancers and gymnasts sometimes fail to maintain good eating habits because they desire to be as thin as possible.
I check a grammar book. it is said that" when the reason is the most important part of the sentence, the because-clause usually comes at the end." but here, I think you can make a choice only after comparing choices. In choice D, readers can understand "they" refer to "young female ballet dancers and gymnasts ", but in choice E, because the clause is close to "habits", the pronoun may refer to them.